Life Lines

Galloping Horses

i-6773a3dd39cf5a72957d396820a69681-Screen shot 2010-10-06 at 8.52.02 PM.pngWho doesn’t love horses? I was just reading a fascinating archived press release from The American Physiological Society about these icons of all western movies.

Researchers John Hermanson, Norm Ducharme and Jonathan Cheetham (Cornell University College of Veterinary Medicine), John Bertram (University of Calgary, College of Medicine), and Michael Butcher (Youngstown State University, Department of Biological Sciences) examined the coordination of movement and breathing in horses (equine). These systems are reported to work in a concerted effort to allow horses to walk, trot, gallop and run.

Ever wonder why horses are prone to injuries during a race? This is because the legs of horses have very long tendons within the forelimbs, which are highly vulnerable to injuries. Dr. Hermanson’s team analyzed these forelimb tendons in horses and found that the superficial digital flexor tendon was responsible for producing a “bouncing” effect for use during trotting and galloping. In contrast, the parallel deep digital flexor tendon moves the horse in a forward direction. Therefore, these tendons must balance each other to allow horses to move. The research team concluded that one cause of injury could result from fatigue of the deep digital flexor tendon resulting from stress and strain on the tendons during a race and may cause the superficial digital flexor tendon to be overloaded.

Where does respiration come in? According to the press release, during running, a horse’s breathing and stride are matched. Their peak airflow is very high (80 liters per second) such that a small problem with breathing can lead to a large problem in movement. There are two cartilages that serve to protect the opening of the airways (larynx) during swallowing. During exercise, these cartilages stay wide open to allow for maximal airflow. However, the nerve that controls the muscle responsible for opening and closing these cartilages is prone to disease or damage. You can imagine that if this nerve is damaged, the cartilages will not open/close properly thereby affecting airflow and also movement.

How did Dr. Hermanson’s team go about helping to ensure that the cartilages stay open even if the nerve is damaged? They developed a pacemaker for the larynx! This pacemaker can stimulate the nerve which activates the muscle controlling the cartilages and keeps them open. The implant is actually capable of keeping the airways of horses running 35-40 miles per hour fully open. This pacemaker research has potential implications for humans who have paralysis of the larynx or have received a laryngeal transplant.

Yet another example of how the field of Comparative Physiology has the potential to benefit humans and animals alike.

Visit The American Physiological Society’s website to view the full Press Release.


  1. #1 Isis the Scientist
    October 19, 2010

    Very cool, Dr. Dolittle! A pacemaker for the larnyx!! Who knew?!?